In applications such as in the production of fibers and films from arylene sulfide polymers, moderately branched to linear poly(arylene sulfide) resins, henceforth PAS, are often preferred over branched types. Furthermore, it is desirable that these moderately branched to linear PAS resins have as high a molecular weight as possible in order to meet specialized product requirements.
While high molecular weight branched PAS resins can readily be produced by the addition of branching agents (e.g., trichlorobenzene) to the polymerization process, moderately branched to linear, high molecular weight PAS resins cannot be made by this method. Previous methods to produce high molecular weight PAS resins without the use of branching agents include air curing the polymer, extracting the low molecular weight fractions from the polymer, and using reaction modifying agents (e.g., alkali metal carboxylates) in the polymerization process. While these previous methods proved to be successful, there exist certain cost and/or physical limitations associated therewith which would not make them available to some who desire moderately branched to linear, higher molecular weight PAS resins. Therefore, it would be beneficial if an improved method of preparation could be devised which results in a moderately branched to linear, high molecular weight PAS.
Linear and non-linear PAS resins can be produced by various processes using polyhalo-substituted aromatic compounds (e.g., dihalobenzenes, trihalobenzenes, dihalobenzophenones and dihaloaromatic sulfones). After the PAS resin is polymerized, the particulate PAS resin must be recovered from the polymerization reaction mixture. There are several conventional means for recovering linear and non-linear PAS resins from a completed polymerization reaction mixture such as, for example, flashing the liquid reaction media or a recovery process referred to as a liquid quench process such as that described in U.S. Pat. No. 4,415,729.
In the liquid quench process, a waste product often referred to as "slime" is produced. This slime generally comprises low molecular weight PAS fines. While the liquid quench process does separate some of this slime material from the more useful, higher molecular weight polymeric material, this separation is not complete. If this slime material (i.e., low molecular weight PAS fines) is not separated from the more useful, higher molecular weight polymeric material, this will result in lowering the molecular weight of the final recovered polymeric product. Therefore, one object of this invention is to provide a process for effectively separating the lower molecular weight polymeric material. This inventive separation process results in substantially increasing the molecular weight of the final recovered polymeric product.
Other aspects, concepts, and objects of this invention will become apparent from the following Detailed Description when considered with the appended claims.